The factor XIII is also referred to as fibrin stabilizing factor. It is a protein playing a part in the promotion of acquiring the resistance to fibrinolysis and forming adhesion carriers of fibroblasts. When activated by thrombin and calcium ion, the factor XIII causes cross-linking reaction between fibrin molecules and between fibrin and other proteins by transglutaminase reaction during the terminal stage of the blood coagulation reaction to form stable fibrin clots and the like. Normally, this protein exists in blood in an inactive form, but when blood coagulation is caused by hemorrhage or the like to form thrombin, it is activated by the action of thrombin and calcium ion to stabilize fibrin.
Therefore, although a normal threshold of blood coagulation time is seen in the case of a decrease or lack in the factor XIII in blood, the resulting fibrin clots are weak and show a tendency to delay healing of wounds in addition to characteristic phenomena such as posthemorrhage and the like. The decrease or lack in the factor XIII are seen in, for example, congenital deficiency, disseminated intravascular coagulation (DIC), serious hepatic diseases, malignant tumor, leukemia, acquirers of a factor XIII inhibitors, major operations or the like. Therefore, the determination of the factor XIII is of importance in diagnosing diseases or evaluating therapeutic effects. It is required to establish a method of determining the factor XIII accurately, quickly and easily.
However, prior art methods of the determination are not satisfactory for this need. The following methods are known as conventional methods of determining the factor XIII: qualitative methods by clot dissolution which test whether clots (fibrin clots) formed by plasma coagulation are soluble in a diluted acid solution (e.g., 1% monochloroacetic acid, etc.) or a urea solution (5-8 mol/l); semiquantitative methods by clot dissolution after antibody neutralization or serial dilution; other immunological methods; quantitative methods by amine uptake utilizing the transglutaminase activity of the active factor XIII (e.g., Nippon Rinsho, vol. 47, a special 1989 number, p. 846-848; Rinsho Kensa, vol. 27, No. 8, p. 848-853 (August 1983)). However, accurate activity of the factor XIII is not determined by qualitative or semiquantitative methods.
Immunological methods wherein an antibody to the factor XIII is used to catch the factor XIII as an antigen (e.g., JP-A 59-192961, JP-A 63-184061) generally need complicated operations and take several hours for the determination. Further, it is problematic in that, because of the determination in terms of an antigenic amount, factor XIII activity in living bodies is not reflected accurately.
As amine uptake methods for the quantitative determination of factor XIII activity, there are the radioisotope method wherein the factor XIII in a sample is activated by thrombin and calcium ion to form the activated factor XIII, followed by incorporation of amine substrates into carbonyl substrates using casein, phenylpropionylthiocholine, butyrylpyrazole or the like as the carbonyl substrate, synthetic substrates such as monodansylcadaverine, putrescine, glycine ethyl ester, histamine or the like as the amine substrate; fluorescence methods (e.g., JP-A 58-216959); the method wherein ammonia formed by amine uptake reaction is introduced to AND or NADP forming reaction using NADH or NADPH and GLDH (glutamate dehydrogenase) and ketoglutarate (Clin. Chem., Vol. 31, No. 1, p. 35-40, 1985; JP-A 1-309700). To inactivate fibrinogen in the sample, these methods need operations of warming at 56.degree. C. for 3 to 4 minutes followed by cooling before the factor XIII is activated. The reaction time for the determination of the activated factor XIII is 10 to 30 minutes, and centrifugal or chromatographic operations are needed after the reaction. Therefore, the operations are complicated and take much time, and there is a problem in the accuracy of the determination. Since the radioisotope method uses radioactive substances and needs a heavy equipment investment and has a severe economical burden.
In the method described in JP-A 1-309700 of the above amine uptake methods, glycine-proline-arginine-proline, a fibrin coagulation inhibitor, is used to remove effects of fibrinogen-fibrin. The formed ammonia is determined using a glutamine-containing peptide such as leucine-leucine-glycine-proline-glycine-glutamine-serine-lysine-valine-iso leucineglycineamide and a primary amine in the presence of the fibrin coagulation inhibitor. This method costs much because a special peptide is used. Further, many reactions are involved in the determination and errors are likely to be caused. Further, ammonia present in the sample can affect the determination.